Settling aid in heavy solvents



Patented Sept. 13, 1938 UNITED} STATES SETTLING AID IN HEAVY SOLVENTSJames M. Whiteley, Roselle, N. J., assignor to Standard Oil DevelopmentCompany, a corporation of Delaware No Drawing. Application June 15,1934,

Serial No. 730,730

3 Claims.

The present invention deals with improved methods for separating waxyconstituents from oils in order to produce oils of low cold test. Theinvention will be fully understood from the following description.

Waxy materials are separated from petroleum oils by various methods, allof which have in common the feature of solidifying the solid wax bychilling to low temperatures. The separation may be efiected bymechanical means such as simple gravity separation, centrifugalsedimentation or filtration, either in ordinary plate or frame pressesor in centrifugal filters.

The present invention deals with the process of separating waxes fromoils, when diluted with solvents of 'the type which are heavier than thesolid waxes themselves, by any of the means disclosed above, while underthe influence of wax modifying agents or separation aids of the typewhich are freely dispersible in the oil. This case is a continuation inpart of the invention disclosed in my co-pending U. S. applicationSerial No. 593,407, filed February 16, 1932.

Among the solvents included in the above class are the halogenatedaliphatic or aromatic hydrocarbons such as carbon tetrachloride,dichlorethane, difluorpropane, tribromethane, dichlorethylene,trichlorpropylene, chlorbenzol or toluol and the like. While thesesolvents may be used alone it is preferred to use them in combinationseither with each other or some other materials such as benzol, toluol,xylol and petroleum naphthas, ranging from propane to octane andheavier. The'solvent is preferably selected so as to have a freezingpoint considerably below thetemperature' at which the wax separation iseffective, also to have as low a solvent power for waxes at theseparation temperature as possible, which makes for the least possiblespread between wax separation temperature and the pour point of theoilproduced. Particularly useful combinations of these types of solventsare as follows:

Per cent Dichlor ethane '75 Carbon tetrachloride 25 Dichlor propane 70Carbon tetrachloride 30 Dichlor ethane 50 Dichlorethylene 50 Dichlorethane 60 Trifiuor ethylene 40 Dichlor ethane '70 Carbon tetrachloride20 Trichlorethylene Dichlor ethane 70 Ben-Z01 --1-- different methods.

Per cent Dichlor propane '75 Toluol Xylol 10 Ethylene difluoride 70Carbon tetrachloride 15 Naphtha 15 When the solvent dissolves the aidcompletely forming a clear solution, the separation aid is almost alwaysof low activity.

The Wax modifiers or separation aids which are used may also be producedby a great many In the first place, I may use small amounts of asphalticmaterials produced particularly for the process, by high temperatureoxidation of petroleum products or obtained from heavy petroleumresidues by precipitation with the known class of solvents, which aremiscible with oils but precipitate the asphalts. Of these may bementioned briefly the light hydrocarbons, particularly those which aregaseous at normal temperatures, and alcohols and ketones although agreat many others are known. These asphaltic materials may also beobtained as residues in the distillation of asphalticbase oils, and atthe same time highly cracked tarry residues may also be employed. Thesemay be added to clean stocks but asphaltic residues furnish their ownmodifiers. The materials which have been mentioned above are not thebest materials which have been found because they are generally toosoluble but theymay be used in the present process in combination withthe heavy solvent where the composition is adjusted carefully to preventcomplete solubility. This process yields an oil of low pour point whichis not raised substantially by subsequent acid, clay or other types ofrefining.

A second class of the wax modifying agents consists of those derivedfrom. parafiin wax, and these may be produced by chlorination of the waxto 10 or 15%, followed by condensation of the chlorinated paraffin aloneor in the presence of aromatic hydrocarbons such as benzol ornaphthalene through the influence of polymerizing catalysts of the typeof aluminum chloride. If desired, the original chlorinated wax may bedechlorinated by raising the temperature soas to split off hydrochloricacid and leave a mixture of monoand dior even tri-olefines-of the wax,which preserves substantially the original a simple alkylation butappears to be a combina-,

tion of polymerization and alkylation. These materials are veryeffective although they form clear solutions in the solvent mixtures.

Condensation products may be produced directly from wax by the effect ofhigh voltage, high frequency, electric discharges. This action is wellknown at the present time and results in a polymer which may be raisedto almost any desired degree of polymerization. The heaviertypes ofpolymers are very effective for the present purposes and like the onesabove form clear solutions.

Another class of these modifying agents is obtained from highly crackedoils such as Burton still or tube and tank tar. It is preferable to useheavy high boiling distillates from these materials and to treat themwith condensing catalysts of the type of aluminum chloride underspecific conditions. After the treatment these materials are separatedfrom the sludge and may berecovered either as heavy liquid or as solidmaterial. These substances are specifically described in a co-pendingapplication, Serial Nos. 645,232 and 645,233, filed December 1, 1932.

Polymers which are suitable for the present purpose may be obtained fromthe distillation residues of high boiling, oxygen containing, organicmaterials which do not distill without leav-- ing pitchy residues. Inparticular organic materials characterized by long hydrocarbon chains,with more than 10 or preferably more than 15 carbon atoms, from theclass of alcohols, ketones, esters, aldehydes, acids and the like. Theglycerides, heavy fatty acids, both saturated and unsaturated orhydro-xylated, are especially desirable for the purpose as are also theresidue on distillation of oxidation products of paraffin wax. Thesevarious materials are distilled and the residues left behind are thepolymers which are used for the present purpose. ,Stearine pitch, cottonseed oil pitch and various fatty acid pitches and similar materials areexcellent examples of this particular class of substances.

A still further class of substances having this property comprises thepolyvalent metal soaps such as aluminum stearate, lead, nickel, zinc andmagnesium stearate, and other soaps of natural acids as well as thecorresponding soaps produced from acids derived by the oxidation of waxyhydrocarbons.

These are other materials which have this property to some degreeincluding degras and lanolin, esters of the alkylol amines such astriethanol amine, and similar materials.

Any of the above mentioned modifying agents may be used and may be addedto the oil before or after addition of the solvent. The mixture ispreferably stirred carefully to obtain homogeneity and heating may beemployed so as to make the mixing complete. a a

The amount of modifying agent required varies considerably with theparticular type of agent employed, and withthe concentration of theactive material in the particular agent. Ordinarily, it is suificient touse from .01 to 5.0% but as indicated before, such figures varyaccording to the care and method of producing the particular modifyingagent. In any case, the material is added in a relatively minute amountand ordiwith the minimum cost of equipment.

narily shows no substantial effect on the oil after treatment.

' The diluted oil is then chilled to the wax separation temperature andthis may be done slowly according to ordinary procedure or it may bedone rapidly, the modifying agents, having the property of allowing thechilling to be effected at very rapid rates which might be termed shockchilling. Among the methods which can be used may be mentioned theevaporation of a part of the solvent effected by pulling a relativelyhigh vacuum on the vessel in which the solvent diluted oil ismaintained. In this manner the temperature of the oil may be reduced atrates of 25 to 50 F. per hour, or even greater. It should be understoodthat this is not the only method that can be used but any other means ofreducing the temperature, for example, by external cooling, using brine,ammonia or the like are perfectly satisfactory.

The separation itself as indicated before may be effected by filtrationin the ordinary plate and frame presses or continuous rotary filters nowused for the filtration of waxy oils. The use of filtration aid effectsa rapid flow and clear filtration. The waxy cake is considerably drierthan ordinarily produced and the yield of oil is larger by several percent than when the separation aid is not used.

The separation may be accomplished in rotary or centrifugal filters ofthe type disclosed in the copending application 669,084 filed May 3,1933, in the names of Murphree and Reeves, with the same advantages asnoted above.

The separation may also be effected by cold settling, which is merelygravity separation, or by'centrifugal means, in which the effect ofgravity is greatly'increased. The separation may be effected in a seriesof steps, for example with intermediate cooling to successively lowertemperatures and the mode of separation in these stages may all besimilar or they may be different. There may be combinations offiltration steps with settling or centrifugation. One particularlydesirable combination of steps consists in chilling and settling in thepresence of a separation aid so'as to obtain a large proportion of theoil which can be drawn off below the waxy layer. The oily-solvent layermay be filtered or otherwise treated, where desired, but ordinarily itis of sufiiciently low pour point so as to be used directly. 'The'waxylayer, which, of course, contains considerable amounts of oil andsolvent may be filtered, say by means of a continuous rotary filter, orcentrifuged. This method gives high yields The filter or centrifuge,which can be used if desired, is considerably smaller than necessary ifthe entire quantity of waxy oil is passed through it.

- The oils treated by the present methods'are of any type whatsoever. Asindicated before, the

heavy solvents, particularly chlorinated or other halogenated solvents,are capable of handling separation aids or wax modifies are freelysoluble in the oils at elevated temperatures, and their action appearsto be of an entirely different type from the earths which are insolublein oils at any temperatures.

In order to illustrate the operation of my invention, the followingexamples are presented. In each of these experiments the separation iseffected by cold settling advisedly because the effect may be moreclearly estimated in numerical quantities. However, it will be fullyunderstood that equal improvements are wrought where the separation isaccomplished by centrifugal sedimentation or by filtration.

1. In the following comparative tests the oil used was an overhead stockhaving a '75 second Saybolt viscosity at 210 F. This oil was mixed witha solvent comprising 25% of C014 and 75% of dichlorethane. Theseparation aid added in this test was one produced by the condensationof parafiin wax chlorinated to about 12% by weight of chlorin with about10% of naphthalene. The condensation was efiected at a temperature ofabout 100 F. with aluminum chloride. The amount of the separation aidvaried as shown in the following table. The experiments consisted inplacing 200 c. c. of the oil solvent mixture,- which had been chilled toa wax separation temperature of 20 F. and which were thoroughly mixed ingraduated cylinders. The blank sample containing no separation aid andthe samples containing the various amounts of the condensation productwere observed at intervals and the figures in the table indicate theamount of clear liquid which was separated. It will be understood thatthe wax was lighter in specific gravity than the oil solvent mixture sothat the wax gathered at the top of the tube in each case.

Amount of the wax modifier Blank 002% Hours 0 2. The test outlined inExample 1 is repeated with residual stock having an 81 second SayboltViscosity at 210 F. The conditions of the experiment were substantiallythe same and the results are shown in the table below.

Amount of the waa: modifier Eours 0% 0. 04% 0. 08% 0. 16%

c c 6.0. c c. c c

3. In an experiment similar to that quoted above the settling rate of ablank sample and one oil in both cases was a distillate having aviscosity of 1'70 seconds Saybolt at 210 F. The solvent was 75% dichlorethane and 25% carbon tetrachloride and is used in proportion of 3volumes of the mixed solvent to 1 of oil. Separation temperature is 22F. The aid used in the experiment was an asphaltic polymer produced bythe action of aluminum chloride in a heavy distillate from a crackingcoil tar.

Sample aid used 4 hours 72 hours Percent O 35 It will be seen that thedegree of separation is much more rapid and complete when the separationaid is used.

4. The following experiment was carried out to illustrate the settlingpower of voltolized wax. The oil is the same as used above and thesolvent is the same.

Volume of Percent of clean 011 Sample sepirizgung Separated in 16 hoursPercent Percent Blank 0 50 Blank and voltolized paraffin wax M. 1.

150 F 1 78 Blank and voltolized paraffin wax M. P.

from hydrocarbon oils which comprises diluting the oil with a solventcomprising a halogenated hydrocarbon heavier than wax in an amount atleast sufficient to make the specific gravity of the-mixture greaterthan that of wax, adding a wax modifying agent produced by condensationof active derivatives of paraffin wax which are prepared by chlorinatingparaffinwax and then dechlorinating the same by heating to split offhydrochloric acid, leaving the carbon structure substantially unchanged,chilling the oil-solvent mixture to cause the wax to solidify andseparating the solidifiedwax.

2. Process according to claim 1 in which the wax modifying agent is apolymer of the class produced from chlorinated wax and aromatichydrocarbons.

3. Process according to claim 1, in which the wax modifying agent isproduced as a condensation product of active derivatives of paraffin waxselected from the class of chlorinated waxes and the olefines derived bydechlorination.

JAMES M. WHITELEY.

